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Fluorous zirconium phosphonates as novel materials for catalyst separation and recovery

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posted on 15.12.2014, 10:35 authored by James Andrew Bennett
Amorphous fluorous zirconium phosphonates (FZrP) with varying degrees of fluorination have been successfully synthesised and their ability to recover fluorous catalysts assessed in three catalytic systems; a dirhodium perfluorobutyrate cyclopropanation of styrene, a perfluorooctyl seleninic acid oxidation of p-nitrobenzaldehyde and a fluorous BINAP palladium catalyst enantioselective fluorination of methyl and butyl cyclopentanone-2-carboxylate.;Conversions of 60 -- 70% were attained for the cyclopropanation of styrene after 4 hours in toluene at 100°C using 0.017 mol% of dirhodium perfluorobutyrate. The catalyst was recovered up to 6 times in both supported and homogeneous/solid phase extraction systems, with no observable drop in activity. Rhodium leaching levels were lowest when the catalyst was supported on [Zn(O3P-C6H4-C6F13)2]. A solid-supported seleninic acid precatalyst for the oxidation of p-nitrobenzaldehyde was recycled 3 times under optimised conditions, with accumulative Se leaching of 2.0%. Conversions fell slightly over the 3 runs, from 94 to 82%. A comparison of support materials showed that, as for the rhodium system, catalyst leaching was lowest with the FZrP material, [Zr(O3P-C6H4-C6F13) 2].;In the enantioselective fluorination system, the Pd BINAP catalyst was most effectively separated and reused using a column of FZrP. The catalyst was recycled over 3 runs, with conversions over 90% and ees in excess of 88%. Due to further purification of the product by column chromatography, necessary for chiral-GC analysis, ICP-OES analysis was not performed and Pd leaching data was, therefore, unavailable for this system.


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University of Leicester

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